riscv: cacheinfo: Add back init_cache_level() function

commit 5944ce09 (arch_topology: Build cacheinfo from primary CPU)
removed the init_cache_level() function from arch/riscv/kernel/cacheinfo.c
and relies on the init_cpu_topology() function in drivers/base/arch_topology.c
to call fetch_cache_info() which in turn calls init_of_cache_level() to
populate the cache hierarchy information. However, init_cpu_topology() is only
called from smpboot.c:smp_prepare_cpus() and thus only available when
CONFIG_SMP is defined.

To support non-SMP enabled kernels to still detect cache hierarchy, we add back
the init_cache_level() function. The init_level_allocate_ci() function handles
this gracefully on SMP-enabled kernels anyway where fetch_cache_info() is
called from init_cpu_topology() earlier in the boot phase.
Signed-off-by: Steffen Persvold <spersvold@gmail.com>
Link: https://lore.kernel.org/r/20240707003515.5058-1-spersvold@gmail.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/cacheinfo.c

@@ -71,6 +71,11 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
 	this_leaf->type = type;
 }
 
+int init_cache_level(unsigned int cpu)
+{
+	return init_of_cache_level(cpu);
+}
+
 int populate_cache_leaves(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);